This is a proposal to purchase a Cell Sorter/Flow Cytometer to be shared by many investigators at the University of Washington. Twenty-two investigators participate in this proposal, describing their need for additional Cell Sorting Instrumentation. The present shared facility was established in 1980 and has utilized an Ortho Model 50 cell sorter during this entire period. Presently, needs for utilization of this instrument greatly exceed its availability, even with current operation 12hrs a day. The Ortho Sorter is unfortunately also becoming aged and less reliable; failure and needed repair is becoming more frequent and results in loss of experimental data and unavoidable failure to perform scheduled experiments. The only other cell sorter available on campus is rapidly about to become saturated by expansion of faculty and large new projects within that department. A newly designed Cell Sorter has been developed by Coulter Corp (one of the two U.S. manufacturers of these instruments). This new model represents a great improvement in software user-interaction and usage of economical and reliable low-power lasers. We supported investigators at the University of Washington.